An apparatus of known type for conversion of thermal energy by an organic Rankine cycle (ORC) generally comprises: at least one heat exchanger exchanging heat between a high-temperature source and a working fluid, so as to heat, evaporate (and possibly superheat) the working fluid; at least one turbine fed by the vaporised working fluid outflowing from the heat exchanger so as to carry out conversion of the thermal energy present in the working fluid into mechanical energy according to a Rankine cycle; at least one generator operatively connected to the turbine, in which the mechanical energy produced by the turbine is converted into electric energy; at least one condenser where the working fluid coming out of the turbine is condensed and sent to at least one pump; from the pump the working fluid is fed to the heat exchanger.
Turbines of known type for high-molecular-weight gas and vapour expansion are for example described in public documents U.S. Pat. No. 4,458,493 and WO 2010/106570. The turbine disclosed in U.S. Pat. No. 4,458,493 is of the multistage type where a first axial stage is followed by a radial centripetal stage. The turbine disclosed in document WO 2010/106570 on the contrary is of the axial type and comprises a box with a peripheral volute for transit of a working fluid from an inlet to an outlet, a first stator and possible other stators, a turbine shaft rotating about an axis and carrying a first rotor and possible other rotors. A tubular element extends in cantilevered fashion from the box and is coaxial with the turbine shaft. A supporting unit is positioned between the tubular element and the turbine shaft and is extractable all together from the tubular element, except for the shaft.
More generally, the types of known expansion boxes presently in use for thermodynamic ORC cycles are of the axial, one-stage and multi-stage type and of the radial one-stage and multi-stage centripetal or inflow type.
Document WO 2011/007366 shows a turbine used in the field of ORC thermodynamic cycles for generation of energy comprising three radial stages disposed axially after each other.
Document EP 2 080 876 shows a turbomachine, in particular a multi-stage turbocompressor comprising two turbines, one of which is a radial-inflow turbine, and two compressors.
Document U.S. Pat. No. 1,488,582 illustrates a turbine provided with one high-pressure portion and one low-pressure portion in which the fluid flow is gradually deviated from an axial direction to a radial direction.
Document US 2010/0122534 shows a closed or endless circuit system for energy recovery comprising a radial-inflow turbine.